The invention relates to a method of recording data on a photographic film.
The invention can be used for recording time and/or measuring data in photographic traffic monitoring installations.
Photographic traffic monitoring installations, by means of a photographic camera, document violations of traffic regulations. The photographic camera provides a photograph of a traffic scene with a vehicle under observation. Furthermore, data are generated giving, for example, time and location of the taking of the photograph, and the measured speed. Also these data have to be documented or recorded conclusively. This is done by reflecting the data into the photographic picture or by otherwise recording the data to the film.
U.S. Pat. No. 5,041,828 discloses an example of a traffic monitoring installation.
U.S. Pat. Nos. 5,603,227 and 3,849,784 disclose photographic trafic monitoring devices by which an image of instruments showing time and/or speed is generated in a corner of the taken photograph by means of an auxiliary lens and a reflecting prism.
German patent 3,034,161 discloses a photographic camera with an optical writing head. The optical writing head has a LED-matrix which is imaged on the margin of the film. The data to be recorded, such as the time and date when the photograph was taken, are converted to a set of binary energizing signals. These signals consecutively energize the LEDs (light emitting diodes) of the LED-matrix during the feeding of the film. Thereby alphanumeric characters are consecutively generated by the LED-matrix and are recorded on the film margin as written information. According to German patent, there is a two-dimensional array of LEDs, i.e. a LED-matrix, which generates the complete characters one by one.
Instead, the optical writing head may also use a linear array of LEDs, whereby each character is composed of consecutively xe2x80x9cprintedxe2x80x9d colums.
Such photographic recordings on the film cannot be manipulated. Therefore they are acknowledged as evidence in court trials.
Furthermore, scanners are known for scanning the photographs made by a traffic monitoring installation and to convert the photograph to a xe2x80x9cdigital picturexe2x80x9d. By such a scanner, a brightness value in digital form is provided for each picture element (pixel). To this end, the picture on the photographic film is imaged on an image resolving sensor, which contains either a two-dimensional array of sensor elements or a line of sensor elements by which the picture is scanned line-by-line. Such xe2x80x9cdigital picturesxe2x80x9d can then be subjected to picture processing, for example in order to automatically read the licence plate of a photographed vehicle.
When the photograph is scanned, also the data reflected into the photograph or applied to the margin of the film have to be read. Picture processing programs exist which permit a computer to xe2x80x9creadxe2x80x9d a writing scanned as a picture pixel-by-pixel, i.e. convert this writing to the binary code words associated with the various characters. In practice, this reading of the small characters applied to the film margin presents problems. There are reading errors. Such reading errors jeopardize the operability of the whole system, as the data, like the measured speed in a traffic monitoring installation, are highly relevant for imposing a fine to the driver or, maybe, for prosecuting the driver for reckless driving. It has been attempted to solve this problem by adding a test sum to the data, this test sum indicating reading errors. The result of this, however, is, at most, that misread pictures are discarded and not processed further.
It is an object of the invention to make the reading of data which have been applied to a photographic film more reliable.
To this end, in addition to a numeric or alphanumeric representation of the data, an additional field is provided on the film.
Thus, the data is applied to the film, on one hand, in a human-readable format as letters or numbers. On the other hand, the data is additionally applied to the film in another format which simplifies reading of the data and makes it more reliable. Reading errors can be virtually avoided.
An embodiment of the invention is described below with reference to the accompanying drawings.